Fin-stabilized projectiles such as mortar shells are generally fired by inserting them from above into the barrel of the weapon. The projectile has an ogival body having a tail section and slips through the barrel to its lower end. Upon reaching the lower end of the barrel, the projectile firing pin strikes the firing pin of the weapon thereby igniting an ignition cartridge disposed in the projectile tail section.
Known ignition cartridges include a particulate propellant charge disposed around a flash tube. The ignition cartridge with its flash tube fits into the boom portion of the tail section which also carries stabilizing fins. The flash tube has a plurality of holes through which the igniting gases pass to ignite the particulate propellant charge. The energetic propellant charge material begins to combust as gaseous flames move through the flash tube along the length of the ignition cartridge. Throughout the combustion process, flames escape through the plurality of holes and ignite the particulate propellant material surrounding the flash tube.
The boom portion contains the ignition charge and includes propellant gas ejection holes through which propellant gases pass into the barrel of the weapon to propel the projectile out of the barrel. Further charge increments may surround the boom portion and be ignited by the propellant gases being ejected out of the boom holes. The pressure created in the barrel by the propellant gases propel the projectile out the barrel of the weapon.
The gaseous flames emerging from the holes in the boom portion should be uniform to equally distribute propellant gases into the barrel behind the projectile. Furthermore, the gas ejection holes are of a size sufficient to burn through and penetrate other materials, such as the covering material of increment charges externally disposed on the tail boom portion. To make such needle-like flame shapes, a small hole for the flame is required, thereby increasing the pressure created upon ignition causing a corresponding increase in the possibility of an explosion that may rupture the boom portion of the tail section.
Flake powder propellant is generally universally used in combination with the flash tube configuration in known ignition cartridges for fin-stabilized projectiles. There are dangers attendant the possibility of the boom portion to fracture causing the projectile to fall short and/or fly erratically. Presently, the hydrostatic pressure testing of one hundred percent (100%) of all tail section boom portions makes sure that they are strong enough to withstand the explosion pressures developed within them upon setting off the prior art ignition cartridge.
The following U.S. Pat. No. 2,434,652; 3,182,595; 3,429,264; 4,094,248; 4,876,962; and 4,922,823 disclose various types of solid shapes used in various other types of shells.
U.S. Pat. No. 3,182,595 discloses the use of benite strands in igniter assembly used for high velocity anti-tank projectiles. This patentee makes an improvement in the extruded form of black powder by substituting a material referred to as benite. Nothing in this patent relates to the use of solid propellant strands for propellant load package in a fin-stabilized projectile fired by dropping the projectile into the open barrel of the weapon.
U.S. Pat. No. 4,876,962 discloses the use of a propellant charge for cannons for the purpose of providing an extremely high charged density and high progressivity with respect to such cannon ammunition. The patentee in this case does not address the igniting of an external solid increment propellant charge using an igniting load package in a fin-stabilized projectile.
U.S. Pat. Nos. 2,434,652; 2,697,325; 3,677,010 each show solid propellant materials used in firing rockets. Here, the progressive burning of the solid propellant from one end to the other is important in producing rocket movement. Nothing in these disclosures teach how to overcome the inherent problems existing with igniting particulate ignition cartridges having a flash tube.
U.S. Pat. Nos. 660,567; 660,568; 3,429,264 and 4,094,248 disclose various methods of forming solid propellant materials. However, none of these patents address the question of improving the firing of fin-stabilized projectiles from muzzle-loaded weapons.